TECHNICAL FIELD
[0001] The invention relates to a polymer composition for manufacturing a small to medium-sized
container, the polymer composition including a high-density polyethylene recovered
from a secondary battery separator, and to a small to medium-sized container manufactured
from such a polymer composition.
BACKGROUND
[0002] As the use of a secondary battery becomes more and more abundant, the number of waste
secondary batteries, which are discarded at the end of their lifespan, is increasing.
Various methods for recycling such waste secondary batteries are hence being studied
recently, including pre-processing work like recovering, discharging, crushing and
sorting, thereby classifying different parts of the waste secondary batteries like
outer cans, separators or electrodes. For metals such as cobalt, nickel, lithium and
manganese, processes of recovery from these parts are available.
[0003] However, polymers of separators recovered from the waste secondary batteries or from
defective products, or from separator scraps produced during a manufacturing process
are presently not recycled, but incinerated or crushed and sometimes exported overseas,
and have thus been identified as a cause of environmental pollution.
[0004] Various efforts to recycle polymers of waste separators have been attempted, but
due to difficult physical properties and processability, it is necessary to perform
adjustments to make the materials appropriate for use and further processing in molding
methods.
[0005] More specifically, since separators are typically made from polyethylene, various
products may, in principle, be molded using the polyethylene recovered from waste
separators. These include small to medium-sized containers. These containers are required
to have a high standard in mechanical properties such as crack resistance, tensile
strength, and flexural modulus, and the polymer materials must be readily processabile
for efficient workability. However, while polyethylene recovered from waste separators
typically has excellent impact strength, it typically has a poor crack resistance
and insignificant elongation and flexural modulus. It also typically has bad processability
due to a low melt index, and thus, it is difficult to mold.
[0006] The problem to be solved by the present invention is the development of an environmentally
friendly polymer composition, which includes a polyethylene recycled from a waste
separator, has excellent processability so that it may be molded into products of
various forms, and lead to products of excellent mechanical properties
SUMMARY
[0007] Against this background, the present invention is directed to a polymer composition
for manufacturing a container, preferably a small to medium-sized container, the composition
including a high-density polyethylene recovered from a secondary battery separator,
the composition having excellent mechanical properties such as flexural modulus, tensile
strength at yield, and elongation, and having excellent processability.
[0008] In this invention, a small to medium-sized container is preferably one having a capacity
of less than 50 L, preferably less than 20 L.
[0009] In addition, the present invention is directed to a small to medium-sized container
manufactured by molding such a polymer composition.
[0010] Further, the present invention is directed to a method of recycling a waste separator
of a secondary battery to prepare such a polymer composition and to manufacture a
small to medium-sized container having excellent mechanical properties by molding
the polymer composition.
[0011] According to the invention, a polymer composition in agreement with claim 1 for manufacturing
a small to medium-sized container is provided. The polymer composition includes a
high-density polyethylene recovered from a secondary battery separator. It was found
that when a new material satisfying certain conditions is included, a polymer composition
having excellent mechanical properties such as processability, flexural modulus, tensile
strength at yield, and elongation in manufacturing a small to medium-sized container
may be prepared.
[0012] More specifically, a polymer composition according to the invention includes: a first
high-density polyethylene; and a second high-density polyethylene having a density
of 0.930 to 0.970 g/cm
3, wherein the polymer composition satisfies the following Equation 1:

[0013] wherein
x is a weight percentage of the first high-density polyethylene in the polymer composition
for manufacturing a small to medium-sized container, y is a weight percentage of the
second high-density polyethylene in the polymer composition for manufacturing a small
to medium-sized container,
MIa is a melt flow index of the first high-density polyethylene, is measured in accordance
with ASTM D1238 (190°C, 2.16 kg); and MIb is a melt flow index of the second high-density polyethylene, as measured in accordance
with ASTM D1238 (190°C, 2.16 kg).
[0014] In one embodiment, the first high-density polyethylene recovered from the secondary
battery separator has a melt flow index of 0.01 to 0.20 g/10 min as measured in accordance
with ASTM D1238 (190°C, 2.16 kg).
[0015] In one embodiment, the first high-density polyethylene recovered from the secondary
battery separator has a flexural modulus of 5,000 to 15,000 kg/cm
2, a tensile strength at yield of 200 to 400 kg/cm
2, and an elongation of 300% or more, when measured by methods as described further
down in the description.
[0016] In one embodiment, the polymer composition includes 20 to 60 wt% of the first high-density
polyethylene and 40 to 80 wt% of the second high-density polyethylene.
[0017] In one embodiment, the polymer composition satisfies the following Equation 1-1:

[0018] In one embodiment, the melt flow indices of the first high-density polyethylene (MI
a) and the second high-density polyethylene (MI
b), when measured in accordance with ASTM D1238 (190°C, 2.16 kg), satisfy the following
Equation 2.

[0019] In one embodiment, the second high-density polyethylene has a melt flow index of
0.25 to 1.5 g/10 min, when measured in accordance with ASTM D1238 (190°C, 2.16 kg).
[0020] In one embodiment, the second high-density polyethylene has a polydispersity index
(PDI, Mw/Mn) of 6 or more, when measured as described further down in the description.
[0021] In one embodiment, the second high-density polyethylene has a flexural modulus of
9,000 kg/cm
2 or more, when measured as described further down in the description.
[0022] In one embodiment, the polymer composition has a melt flow index of 0.1 to 0.5 g/10
min, when measured in accordance with ASTM D1238 (190°C, 2.16 kg).
[0023] In one embodiment, the polymer composition has a tensile strength at yield of 240
kg/cm
2 or more and an elongation of 300% or more, when measured by methods as described
further down in the description.
[0024] In one embodiment, the polymer composition has an environmental stress crack resistance
of 30 hours or more, when measured in accordance with ASTM D1693.
[0025] In one embodiment, the polymer composition has an Izod impact strength measured at
a temperature of 23±2°C of 20 kgf.cm/cm or more and a flexural modulus of 10,000 kg/cm
2 or more, when measured by methods as described further down in the description.
[0026] The invention further relates to pellets for molding, the pellets including a polymer
composition according to the invention.
[0027] Further, the invention relates to a container, preferably a small to medium-sized
container, manufactured by molding the polymer composition according to the invention.
[0028] Yet further, the invention relates to a method of manufacturing a container, preferably
a small to medium-sized container, the method including: (a) recovering a first high-density
polyethylene from a secondary battery separator and selecting a second high-density
polyethylene;
(b) preparing a pre-molded body from a polymer composition including the first high-density
polyethylene and the second high-density polyethylene; and
(c) molding the pre-molded body to manufacture the container,
wherein the second high-density polyethylene has a density of 0.930 to 0.970 g/cm3, and
the polymer composition satisfies Equation 1 as defined above.
[0029] In one embodiment, in step (a), the secondary battery separator is any one or two
or more waste separators selected from the group of: waste separators obtained by
removing inorganic coating layers from separators recovered from waste secondary batteries
or secondary battery defective products; scraps produced in a secondary battery separator
manufacturing process; or separator ends recovered after trimming.
[0030] In one embodiment, in step (c), the molding is performed by injection molding, blow
molding, or extrusion molding.
[0031] Other preferred features and aspects of the invention are described in the following
detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is an image of small to medium-sized molded articles manufactured by blow
molding polymer compositions of Examples 1 to 3.
DETAILED DESCRIPTION OF EMBODIMENTS
[0033] In the following, units used in the present specification without particular mention
are based on weights, and as an example, a unit of % or ratio refers to a wt% or a
weight ratio and wt% refers to wt% of any one component in a total composition, unless
otherwise defined.
[0034] The term "small to medium-sized container" used in the present specification may
include a small to medium-sized structure used in daily life such as a product container
of less than 20 L, a daily necessities case, an airtight container and a plastic bottle/canister.
[0035] A polymer composition according to the invention, which can be used for manufacturing
a small to medium-sized container, includes: a first high-density polyethylene, that
has been recovered from a secondary battery separator; and a second high-density polyethylene
having a density of 0.930 to 0.970 g/cm
3, wherein the polymer composition satisfies the following Equation 1. In a preferred
embodiment, the polymer composition satisfies the following Equation 1-1:

[0036] In the equations, x is a weight percentage of the first high-density polyethylene
in the polymer composition for manufacturing a small to medium-sized container, y
is a weight percentage of the second high-density polyethylene in the polymer composition
for manufacturing a small to medium-sized container, MI
a is a melt flow index of the first high-density polyethylene, MI
b is a melt flow index of the second high-density polyethylene, the melt flow indices
being measured in accordance with ASTM D1238 (190°C, 2.16 kg).
[0037] The secondary battery separator may be any one or two or more waste separators selected
from waste separators obtained by removing inorganic coating layers from separators
recovered from waste lithium secondary batteries and secondary battery defective products,
scraps produced in a secondary battery separator manufacturing process, separator
ends recovered after trimming, and the like. When taken alone, the first high-density
polyethylene recovered from the secondary battery separator described above (hereinafter,
first high-density polyethylene) may have a bad processability due to a low melt index
and has insignificant mechanical properties such as elongation and flexural modulus,
so that it is difficult to recycle it, but the polymer composition for manufacturing
a small to medium-sized according to an exemplary embodiment, though including the
first high-density polyethylene, may implement excellent processability and excellent
mechanical strength.
[0038] The first high-density polyethylene may have a weight average molecular weight (Mw)
of 100,000 to 1,000,000 g/mol, specifically 150,000 to 700,000 g/mol, and more specifically
200,000 to 500,000 g/mol, when measured by a method as described further below. The
number average molecular weight (Mn) of the first high-density polyethylene may range
between 10,000 to 500,000 g/mol, specifically 20,000 to 400,000 g/mol, and more specifically
30,000 to 300,000 g/mol, when measured by a method as described further below. The
polydispersity index (PDI) of the first high-density polyethylene may range between
2 to 30, specifically 3 to 25, and more specifically 4 to 20, when measured by a method
as described further below.
[0039] The first high-density polyethylene may have a melt flow index of 0.001 to 0.5 g/10
min, specifically 0.01 to 0.20 g/10 min, and more specifically 0.01 to 0.10 g/10 min,
when measured in accordance with ASTM D1238 (190°C, 2.16 kg).
[0040] The first high-density polyethylene may have a density of 0.920 to 0.990 g/cm
3, specifically 0.930 to 0.970 g/cm
3, and more specifically 0.940 to 0.960g/cm
3.
[0041] The first high-density polyethylene may have a melting point (T
m) of 100°C or higher, specifically 120°C or higher, and more specifically 130°C or
higher, when determined by DSC according to ASTM D3418.
[0042] The first high-density polyethylene may have a tensile strength at yield of 150 to
450 kgf/cm
2, specifically 200 to 400 kgf/cm
2, and more specifically 220 to 350 kgf/cm
2, when determined as explained further below.
[0043] IThe first high-density polyethylene may have an elongation at break of 300% or more,
specifically 350 to 2000%, and more specifically 400 to 1500%, when determined as
explained further below.
[0044] The first high-density polyethylene may have a flexural modulus of 2,000 to 25,000
kg/cm
2, specifically 3,000 to 20,000 kg/cm
2, and more specifically 5,000 to 15,000 kg/cm
2, when determined as explained further below.
[0045] The first high-density polyethylene may have an Izod impact strength at room temperature
(23±2°C) of 50 kgf.cm/cm or more, specifically 80 kgf.cm/cm or more, when determined
as explained further below. Though the upper limit is not largely limited, the first
high-density polyethylene may have an Izod impact strength of 200 kgf.cm/cm or less,
when determined as explained further below.
[0046] The second high-density polyethylene may have a weight average molecular weight (Mw)
of 50,000 to 500,000 g/mol, specifically 80,000 to 400,000 g/mol, and more specifically
100,000 to 300,000 g/mol, when determined as explained further below. The number average
molecular weight (Mn) of the second high-density polyethylene may be from 10,000 to
250,000 g/mol, specifically 15,000 to 200,000 g/mol, and more specifically 20,000
to 150,000 g/mol,, when determined as explained further below.
[0047] The melt flow index of the first high-density polyethylene (MI
a) and the melt flow index of the second high-density polyethylene (MI
b) may satisfy the following Equation 2, specifically Equation 2-1, when measured in
accordance with ASTM D1238 (190°C, 2.16 kg):

[0048] Such melt flow index is appropriate for manufacturing small to medium-sized containers,
thereby implementing more improved work efficiency and a low defect rate.
[0049] In specific embodiments, the second high-density polyethylene, when measured in accordance
with ASTM D1238 (190°C, 2.16 kg), may be 0.1 to 5 g/10 min, specifically 0.25 to 1.5
g/10 min, and more specifically 0.5 to 1 g/10 min.
[0050] In embodiments, the first high-density polyethylene and the second high-density polyethylene
may satisfy both Equation 1 and Equation 2, specifically both Equation 1-1 and Equation
2-1. In this case, the polymer composition shows a melt flow index very preferably
for manufacturing small to medium-sized containers, and furthermore, may effectively
implement excellent mechanical properties such as elongation, flexural modulus, and
impact strength in the container.
[0051] The second high-density polyethylene may have a density of 0.930 to 0.970 g/cm
3, specifically 0.940 to 0.970 g/cm
3, and more specifically 0.950 to 0.970 g/cm
3.
[0052] The second high-density polyethylene may have a polydispersity index (PDI, Mw/Mn)
of 3 or more, specifically 4 or more, and more specifically 5 to 20, when measured
as described further below.
[0053] The second high-density polyethylene may have a melting point (T
m) of 100°C or higher, specifically 120°C or higher, and more specifically 125 to 150°C,
when determined by DSC according to ASTM D3418.
[0054] The second high-density polyethylene may have a tensile strength at yield of 100
to 500 kgf/cm
2, specifically 200 to 400 kgf/cm
2, and more specifically 250 to 350 kgf/cm
2, when determined as described further below.
[0055] The second high-density polyethylene may have an elongation at break of 300% or more,
specifically 350 to 2000%, or 400 to 1500%, and more specifically 400 to 1000%, when
determined as described further below.
[0056] The second high-density polyethylene may have an Izod impact strength at room temperature
(23±2°C) of 1 kgf.cm/cm or more, specifically 5 kgf.cm/cm or more, when determined
as described further below. Though the upper limit is not largely limited, second
high-density polyethylene may have an Izod impact strength at room temperature (23±2°C)
of 200 kgf.cm/cm or less, when determined as described further below.
[0057] The second high-density polyethylene may have a flexural modulus of 5000 to 50,000
kg/cm
2, specifically 7000 to 30,000 kg/cm
2, and more specifically 9000 to 15,000 kg/cm
2 or 9000 kg/cm
2 or more, when determined as described further below.
[0058] The second high-density polyethylene may have a melt flow index of 0.25 to 1.5 g/10
min, and/or a polydispersity index (PDI, Mw/Mn) of 6 or more, and/or a flexural modulus
of 9,000 kg/cm
2 or more.
[0059] The second high-density polyethylene may have an environmental stress crack resistance
(ESCR) of 10 hours or more, specifically 50 hours or more, when determined as described
further below. The upper limit may not be particularly limited.
[0060] The polymer composition including the second high-density polyethylene satisfying
the physical properties described above may have suppressed occurrence of fine powder
or fume to implement excellent process stability, and though including a significant
amount of the first high-density polyethylene recovered from the waste separator,
may show a melt flow index appropriate for manufacturing a small to medium-sized container
with high work efficiency, the container having excellent mechanical properties such
as elongation and flexural modulus.
[0061] Conventionally, a polyethylene was used alone or in combination with other polyethylenes
for recycling polyethylene recovered from the waste separator. In such configurations,
when the polyethylene is included in excess, a high melt flow index and insignificant
mechanical properties are problematic. In order to solve the problems, the present
invention is based on the finding that when a new polyethylene material satisfying
certain conditions is applied, mechanical properties and processability which are
appropriate for a small to medium-sized container can be obtained.
[0062] In one embodiment, the polymer composition may include 20 to 60 wt% of the first
high-density polyethylene and 40 to 80 wt% of the second high-density polyethylene,
specifically 30 to 50 wt% of the first high-density polyethylene and 50 to 70 wt%
of the second high-density polyethylene. When the range described above is satisfied,
the polymer composition may show a melt flow index highly appropriate for manufacturing
a small to medium-sized container with excellent work efficiency, low occurrence of
fine powder or fume to implement excellent process stability, the container having
improved mechanical physical properties. As the content of the first high-density
polyethylene is increased, recycling efficiency is increased, and thus, environmental
goals achieved more effectively.
[0063] The polymer composition, though including 30 wt% or more of the first high-density
polyethylene, may show a melt flow index appropriate for manufacturing a small to
medium-sized container to exhibit excellent work efficiency to produce a small to
medium-sized container having excellent mechanical properties such as Izod impact
strength, elongation, and flexural modulus. The composition including 30 wt% of more
of the recycled high-density polyethylene renders the inventive composition effective
in achieving environmental goals.
[0064] In one embodiment, the polymer composition has a density of 0.930 to 0.990 g/cm
3, specifically 0.940 to 0.980g/cm
3, and more specifically 0.945 to 0.970g/cm
3.
[0065] In one embodiment, the polymer composition has a melt flow index of 0.1 to 1.0 g/10
min, specifically 0.1 to 0.7 g/10 min, and more specifically 0.1 to 0.5 g/10 min,
as measured in accordance with ASTM D1238 (190°C, 2.16 kg). When this range is satisfied,
processability most appropriate for manufacturing a small to medium-sized container
is imparted, leading to improved work efficiency and a low defective rate.
[0066] In one embodiment, the polymer composition has a tensile strength at yield of 180
kg/cm
2 or more, specifically 220 kg/cm
2 or more, and more specifically 250 kg/cm
2 or more or 260 kg/cm
2 or more, when measured as described further below. Though the upper limit is not
particularly limited, the polymer composition may have a tensile strength at yield
of 2000 kg/cm
2 or less, when measured as described further below.
[0067] In one embodiment, the polymer composition has an elongation at break of 300% or
more, specifically 350% or more or 400% or more, more specifically 500% or more, when
measured as described further below. Though the upper limit is not particularly limited,
the polymer composition may have an elongation at break of 2000% or less, when measured
as described further below.
[0068] In one embodiment, the polymer composition has an environmental stress crack resistance
(ESCR) of 10 hours or more, specifically 30 hours or more, and more specifically 50
hours or more or 100 hours or more, when measured as described further below. The
upper limit is not particularly limited. A longer environmental stress crack resistance
is representative for excellent physical properties of the polymer composition.
[0069] In one embodiment, the polymer composition has a tensile strength at yield of 240
kg/cm
2 or more and an elongation of 300% or more, and/or an environmental stress crack resistance
of 30 hours or more.
[0070] In one embodiment, the polymer composition has an Izod impact strength measured at
a temperature of 23±2°C of 10 kgf.cm/cm or more, specifically 20 kgf.cm/cm or more,
and more specifically 20 to 50 kgf.cm/cm, when measured as described further below.
[0071] In one embodiment, the polymer composition has a flexural modulus of 7,500/cm
2 or more, specifically 9,000/cm
2 or more, and more specifically 10,000/cm
2 or more, when measured as described further below. Though the upper limit is not
particularly limited, the polymer composition may have a flexural modulus of 100,000/cm
2 or less, when measured as described further below.
[0072] In one embodiment, the polymer composition has an Izod impact strength measured at
a temperature of 23±2°C of 20 kgf.cm/cm or more, and/or a flexural modulus of 10,000
kg/cm
2 or more.
[0073] In one embodiment, the polymer composition further includes an additive commonly
used in the art, depending on the purpose and the use. For example, the polymer composition
may further include an antioxidant, a UV absorber, a UV stabilizer, a lubricant, a
pigment, a colorant, a filler, a plasticizer, a flow agent, an antistatic agent, a
flame retardant, a slap agent, an antiblock agent, and the like, and the additive
may be included at an appropriate content within a range which does not impair the
targeted physical properties.
[0074] The UV absorber may be a benzotriazine-based or benzotriazole-based UV absorber,
and further, may be mixed with a HALS-based UV stabilizer or primary and secondary
antioxidants such as dibutylhydroxytoluene, nonylphenylphosphite, and dibutylmethylpheno.
[0075] As a non-limiting example, the benzotriazoles-based UV absorber may include 2-(2'-hydroxymethylphenyl)benzotriazole,
2-(2'-hydroxy-3',5'-bis(α,α-dimethylbenzylphenyl))benzotriazole, 2-(2'-hydroxy-3',5'-dibutylphenyl)benzotriazole,
2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole,
and the like, and the benzotriazine-based UV absorber may be, for example, bis-ethylhexyloxyphenolmethoxyphenyl
triazine.
[0076] In addition, the lubricant serves to improve flowability during extrusion molding
and suppress frictional heat, and may be a combination of one or more selected from
hydrocarbon-based, carboxylic acid-based, alcohol-based, amide-based, ester-based
compounds, and mixtures thereof.
[0077] A pellet for molding including the polymer composition as described above is further
proposed by the invention. The pellets are pre-molded bodies cut into a substantially
uniform size and may form a starting material before manufacturing a molded article.
The pellets may be manufactured by extrusion and injection, for example.
[0078] A container, preferably a small to medium-sized container manufactured by molding
the polymer composition as described above, is a further subject of the invention.
The molding may be selected from injection molding, blow molding, or extrusion molding.
The polymer composition may show a melt flow index appropriate for a small to medium-sized
container molding to allow efficient work and may decrease a defective rate during
operation.
[0079] The container may be a small to medium-sized container, or a molded article such
as a low volume container, a container for storage or preservation, an airtight container,
or a packaging container. The container may have excellent physical properties such
as tensile strength at yield, elongation, flexural strength, impact strength, and
ESCR. There is also a significant beneficial environmental impact as the container
is manufactured by recycling the first high-density polyethylene from a secondary
battery separator. The physical properties of the polymer material of the invention
and of the product, for example container obtained from it by molding or the like
melt-based methods, are identical or similar.
[0080] A method of manufacturing a container including using recycled polymer material from
a waste separator of a secondary battery is another subject of the present invention.
[0081] The method of manufacturing a container includes: (a) recovering a first high-density
polyethylene from a secondary battery separator and selecting a second high-density
polyethylene;
[0082] (b) preparing a pre-molded body from a polymer composition including the first high-density
polyethylene and the second high-density polyethylene; and
[0083] (c) molding the pre-molded body to manufacture the container,
[0084] wherein the second high-density polyethylene includes a second high-density polyethylene
having a density of 0.930 to 0.970 g/cm
3, and
[0085] wherein the polymer composition satisfies the following Equation 1:

[0086] wherein
x is a weight percentage of the first high-density polyethylene in the polymer composition,
y is a weight percentage of the second high-density polyethylene in the polymer composition,
MIa is a melt flow index of the first high-density polyethylene, MIb is a melt flow index of the second high-density polyethylene, and the melt flow indices
are measured in accordance with ASTM D1238 (190°C, 2.16 kg).
[0087] In one embodiment, in step (a), the secondary battery separator may be any one or
two or more waste separators selected from the group of the following: waste separators
obtained by removing inorganic coating layers from separators recovered from waste
lithium secondary batteries or secondary battery defective products; scraps produced
in a secondary battery separator manufacturing process; or separator ends recovered
after trimming.
[0088] In one embodiment, step (a) may further include a chemical or physical pre-processing
process for removing impurities from the first high-density polyethylene from the
secondary battery separator.
[0089] In one embodiment, the second high-density polyethylene satisfies Equation 1, specifically
Equation 1-1, or Equation 2, specifically Equation 2-1.
[0090] The container and the polymer composition for manufacturing it is environmentally
friendly because it includes recycling a waste separator for a secondary battery.
Although the first high-density polyethylene recovered from the secondary battery
may by itself be difficult to mold and shows insignificant physical properties, according
to the invention, the second high-density polyethylene selected based on certain conditions
is included, thereby providing a composition suitable for manufacturing a small to
medium-sized container and having excellent processability and mechanical properties.
[0091] In one embodiment, step (b) is a step of manufacturing a pre-molded body for molding
the polymer composition in (c), and specifically, the pre-molded body may be manufactured
in the form of a pellet for molding for extrusion or injection molding, or parison
for blow molding.
[0092] In one embodiment, in step (c), the molding may be performed by injection molding,
blow molding, or extrusion molding, more specifically blow molding. The polymer composition
according to the invention, though including a high-density polyethylene recovered
from a secondary battery separator and having inappropriate physical properties and
processability for the applications envisioned herein, includes the second high-density
polyethylene selected according to certain conditions, thereby achieving processability
appropriate for the applications envisioned herein, in particular for manufacturing
a small to medium-sized container having excellent mechanical properties.
[0093] Hereinafter, the present disclosure will additionally be described in more detail
with reference to the Examples and Comparative Examples.
[0094] Physical properties of the following examples and comparative examples were measured
by the following methods. These methods also form a basis for the definitions of parameters
above.
[Method of evaluating physical properties]
[0095]
- 1. Density [g/cm3]: after a calibration curve of density values with height based on a standard specimen
with known density was created in a linear density gradient tube using a vertical
column, the specimen for measuring a density prepared above was floated in the column,
a height at which the specimen stopped was recorded, which was compared with the calibration
curve, and the density of the specimen was recorded.
- 2. Molecular weight (Mw, Mn) [g/mol]: GPC (Agilent, Infinity 1260) was used to measure
a weight average molecular weight (Mw) and a number average molecular weight (Mn).
A GPC column temperature was 160°C. A solvent used was trichlorobenzene, a standard
was polystyrene, and analysis was performed at room temperature at a flow rate of
1 mL/min. In addition, a polydispersity index (PDI) value was calculated from Mw and
Mn. Other specific conditions are as follows.
- Analysis instrument: three columns (model name: PLgel Olexis available from Agilent
7.5×300 mm, 13 um) and one guard column (model name: PLgel Olexis available from Agilent
7.5×300 mm, 13 um) were connected, a temperature of 160°C and a GPC flow rate of 1
mL/min were set, and a GPC system to which a refractive index detector is connected
(model name: 1260 Infinity II High-Temperature GPC System available from Agilent)
was used
- Preparation of sample: 2 to 5 mg of samples were dissolved using 1 ml of 1,2,4-trichlorobenzene
of 200 ppm of BHT. At this time, the samples were prepared by stirring at 150°C for
4 hours using a preprocessor (Agilent PL-SP 260 VS Sample Preparation System), 200
µL of the produced solution was injected to GPC, and analysis was performed.
- 3. Melt flow index (MI) [g/10 min]: The melt flow index was measured in accordance
with ASTM D1238, as grams eluted per 10 minutes (g/10 min) under the conditions of
190°C, 2.16 kg. In the case of a recycled secondary battery separator product having
a measured value of 0.05 or less, the measurement was performed at 21.6 kg and then
the value was calculated by dividing the value by 95 which is a flow rate ratio (FRR)
factor.
- 4. Tensile strength at yield and elongation (at break) [kgf/cm2, %]: measured in accordance with ASTM D638, Type IV, specifically, measured under
the speed condition of 50 mm/min, after conditioning a specimen having a thickness
of 2.0 mm under the temperature condition of 23°C and the humidity environment of
50% for 40 hours.
- 5. Izod impact strength [kgf.cm/cm]: in accordance with ASTM D256, a specimen was
manufactured under the conditions of Dimension A (10.16±0.05 mm), was conditioned
under the temperature condition of 23°C and the humidity environment of 50% for 40
hours, and then the Izod impact strength at room temperature was measured at a temperature
of 23±2°C.
- 6. Flexural modulus [kg/cm2]: a specimen was conditioned in the temperature condition of 23°C in a humidity environment
of 50% for 40 hours, and the flexural strength was measured in accordance with the
Procedure condition B (0.1 mm/mm/min) of ASTM D790.
- 7. Environmental stress crack resistance (ESCR) [hour]: measured in accordance with
Condition B, F50 (bath temperature: 50°C) of ASTM D1693.
- 8. The value according to the following Calculation Formula 1 was calculated and is
shown in the following Table 3.

[Preparation Example 1]
[0096] Scraps produced in the secondary battery separator manufacturing process using a
high-density polyethylene as a raw material were crushed into a size of approx. 5
cm×5 cm. The scraps were the scrap part remaining after the separator trimming process.
the crushed scraps were processed in an extruder at a processing temperature of 230°C
to obtain pellets. The pellets were sufficiently dried to obtain first high-density
polyethylene pellets. The physical properties of these first high-density polyethylene
pellets were measured and are shown in the following Table 1.
[Examples 1 to 4, and Comparative Examples 1 and 2]
[0097] The polymer compositions prepared according to Table 2 were input to a twin screw
extruder and melt extruded at a processing temperature of 230°C for a sufficient time
to obtain recycled resin pellets The recycled resin pellets were sufficiently dried
and then melt-mixed with a new resin material at a processing temperature of 220°C
to manufacture pellets for molding. The pellets for molding were injected or extruded
to prepare specimen appropriate for each physical property evaluation standard, and
the physical properties were measured and are shown in the following Table 3.
[Table 1]
|
Preparation Example 1 |
A |
B |
C |
D |
E |
F |
MI |
0.02 |
0.6 |
1 |
0.8 |
0.35 |
0.05 |
6.5 |
MIb-MIa |
- |
0.58 |
0.98 |
0.78 |
0.33 |
0.03 |
6.48 |
Density |
0.952 |
0.963 |
0.965 |
0.955 |
0.958 |
0.953 |
0.953 |
PDI |
4.3 |
8.5 |
10 |
8.5 |
14 |
23 |
6.0 |
Tensile strength at yield |
288 |
300 |
240 |
230 |
280 |
260 |
220 |
Elongation |
787 |
1000 |
500 |
600 |
>700 |
970 |
>500 |
IZod |
>60 |
7 |
8 |
<60 |
15 |
20 |
10 |
Flexural modulus |
11000 |
12000 |
12000 |
9000 |
9500 |
9180 |
8500 |
ESCR |
70 |
- |
13 |
>300 |
>600 |
>1000 |
10 |
- A (YUZEX 8300, SK Chemicals Co., Ltd.)
- B (YUZEX 7300, SK Chemicals Co., Ltd.)
- C (YUZEX 3301, SK Chemicals Co., Ltd.)
- D (YUZEX 2520, SK Chemicals Co., Ltd.)
- E (YUZEX 6100, SK Chemicals Co., Ltd.)
- F (YUZEX 7220, SK Chemicals Co., Ltd.) |
[Table 2]
(wt%) |
Preparation Example 1 |
A |
B |
C |
D |
E |
F |
Example 1 |
30 |
70 |
|
|
|
|
|
Example 2 |
30 |
|
70 |
|
|
|
|
Example 3 |
30 |
|
|
70 |
|
|
|
Example 4 |
30 |
|
|
|
70 |
|
|
Comparativ e Example 1 |
30 |
|
|
|
|
70 |
|
Comparativ e Example 2 |
30 |
|
|
|
|
|
70 |
[Table 3]
|
Exampl e 1 |
Exampl e 2 |
Exampl e 3 |
Exampl e 4 |
Compara tive Example 1 |
Compara tive Example 2 |
Calculation Formula 1 |
-0.66 |
-0.51 |
-0.58 |
-0.83 |
-1.42 |
0.06 |
MI |
0.11 |
0.15 |
0.13 |
0.1 |
0.04 |
1.07 |
Density |
0.956 |
0.959 |
0.952 |
0.955 |
0.951 |
0.951 |
Tensile strength at yield |
280 |
275 |
260 |
277 |
240 |
210 |
Elongation (E3) |
600 |
500 |
400 |
500 |
500 |
250 |
IZod |
30 |
25 |
25 |
20 |
35 |
18 |
Flexural |
11400 |
11100 |
10000 |
10000 |
9625 |
8200 |
modulus (FM3) |
|
|
|
|
|
|
ESCR |
65 |
30 |
>100 |
>100 |
>1000 |
35 |
[0098] As apparent from Tables 2 and 3, it could be experimentally confirmed that the polymer
compositions according to the inventive examples, though including 30 wt% or more
the first high-density polyethylene recovered from the secondary battery separator,
show a melt flow index (MI) in a range of 0.1 to 0.5 g/10 min that is considered suitable
for the manufacture of, for example, a small to medium-sized container The physical
properties measured confirm that the thus-manufactured molded articles show beneficial
elongation and flexural modulus, which are significantly improved when compared with
the first high-density polyethylene of Preparation Example 1 per se, as recovered
from the secondary battery separator. The molded articles also exhibit excellent tensile
strength at yield and impact strength. The invention hence provides means to effectively
implement environmental friendliness by upcycling polymer materials from waste secondary
battery separators.
[0099] The physical properties of the product, for example the container, and the physical
properties of the polymer composition according to the invention are identical or
similar to each other. Hence, the polymer compositions according to the invention
may be used to produce, for example, small to medium-sized containers having excellent
physical properties, thereby recycling and upcycling high-density polyethylene recovered
from a secondary battery waste separator.
1. A polymer composition, comprising:
a first high-density polyethylene; and
a second high-density polyethylene having a density of 0.930 to 0.970 g/cm3;
wherein the polymer composition satisfies the following Equation 1:

wherein
x is a weight percentage of the first high-density polyethylene,
y is a weight percentage of the second high-density polyethylene,
MIa is a melt flow index of the first high-density polyethylene, as measured in accordance
with ASTM D1238 (190°C, 2.16 kg); and
MIb is a melt flow index of the second high-density polyethylene, as measured in accordance
with ASTM D1238 (190°C, 2.16 kg).
2. The polymer composition of claim 1, wherein the first high-density polyethylene has
a melt flow index of 0.01 to 0.2 g/10 min, when measured in accordance with ASTM D1238
(190°C, 2.16 kg).
3. The polymer composition of any preceding claim, wherein the first high-density polyethylene
has a flexural modulus of 5,000 to 15,000 kg/cm2, when measured in accordance with the Procedure condition B (0.1 mm/mm/min) of ASTM
D790 after the specimen was conditioned in the temperature condition of 23°C in a
humidity environment of 50% for 40 hours, and a tensile strength at yield of 200 to
400 kg/cm2and an elongation at break of 300% or more, both when measured in accordance with
ASTM D638, Type IV, under the speed condition of 50 mm/min, after conditioning a specimen
having a thickness of 2.0 mm under the temperature condition of 23°C and the humidity
environment of 50% for 40 hours.
4. The polymer composition of any preceding claim, wherein the polymer composition includes
20 to 60 wt% of the first high-density polyethylene and 40 to 80 wt% of the second
high-density polyethylene.
5. The polymer composition of any preceding claim, wherein the polymer composition satisfies
the following Equation 1-1:
6. The polymer composition of any preceding claim, wherein the melt flow indices of the
first high-density polyethylene (MI
a) and the second high-density polyethylene (MI
b), when measured in accordance with ASTM D1238 (190°C, 2.16 kg), satisfy the following
Equation 2:
7. The polymer composition of any preceding claim, wherein the second high-density polyethylene
has the melt flow index of 0.25 to 1.5 g/10 min, when measured in accordance with
ASTM D1238 (190°C, 2.16 kg), and/or a polydispersity index (PDI, Mw/Mn) of 6 or more,
when measured by GPC as specified in the description, and/or a flexural modulus of
9,000 kg/cm2 or more, when measured in accordance with the Procedure condition B (0.1 mm/mm/min)
of ASTM D790 after the specimen was conditioned in the temperature condition of 23°C
in a humidity environment of 50% for 40 hours.
8. The polymer composition of any preceding claim, wherein the polymer composition has
a melt flow index of 0.1 to 0.5 g/10 min, when measured in accordance with ASTM D1238
(190°C, 2.16 kg).
9. The polymer composition of any preceding claim, wherein the polymer composition has
a tensile strength at yield of 240 kg/cm2 or more and an elongation of 300% or more, when measured in accordance with ASTM
D638, Type IV, under the speed condition of 50 mm/min, after conditioning a specimen
having a thickness of 2.0 mm under the temperature condition of 23°C and the humidity
environment of 50% for 40 hours; and/or an environmental stress crack resistance of
30 hours or more as measured in accordance with ASTM D1693.
10. The polymer composition of any preceding claim, wherein the polymer composition has
an Izod impact strength measured at a temperature of 23±2°C of 20 kgf.cm/cm or more,
when measured in accordance with ASTM D256, the measured specimen being manufactured
under the conditions of Dimension A (10.1610.05 mm), conditioned under the temperature
condition of 23°C and the humidity environment of 50% for 40 hours, and/or a flexural
modulus of 10,000 kg/cm2 or more, when measured in accordance with the Procedure condition B (0.1 mm/mm/min)
of ASTM D790 after the specimen was conditioned in the temperature condition of 23°C
in a humidity environment of 50% for 40 hours.
11. A container manufactured by molding the polymer composition of any preceding claim.
12. Pellets for molding, the pellets including a polymer composition according to any
one of claims 1 to 10.
13. A method of manufacturing a container, the method comprising:
(a) recovering a first high-density polyethylene from a secondary battery separator
and selecting a second high-density polyethylene;
(b) preparing a pre-molded body from a polymer composition including the first high-density
polyethylene and the second high-density polyethylene; and
(c) molding the pre-molded body to manufacture a container;
wherein the second high-density polyethylene includes a second high-density polyethylene
having a density of 0.930 to 0.970 g/cm3, and
the polymer composition satisfies the following Equation 1:

wherein
x is a weight percentage of the first high-density polyethylene,
y is a weight percentage of the second high-density polyethylene,
MIa is a melt flow index of the first high-density polyethylene, as measured in accordance
with ASTM D1238 (190°C, 2.16 kg), and MIb is a melt flow index of the second high-density polyethylene, as measured in accordance
with ASTM D1238 (190°C, 2.16 kg).
14. The method of claim 13, wherein in (a), the secondary battery separator is any one
or two or more waste separators selected from the group consisting of: waste separators
obtained by removing inorganic coating layers from separators recovered from waste
secondary batteries or secondary battery defective products; scraps produced in a
secondary battery separator manufacturing process; or separator ends recovered after
trimming.
15. The method of claim 13 or 14, wherein in (c), the molding is performed by injection
molding, blow molding or profile extrusion.